King Bhumibol Adulyadej of Thailand, who turned 81 on Dec. 5, broke with tradition by not addressing the nation on his birthday. The official reason was that he had a sore throat that affected his voice. Indeed, his health is a source of concern among the Thai people, few of whom have known any other monarch. But it is also possible that he decided this was not a good time to make a public speech, which could be interpreted as a political signal of his approval or disapproval of the various factions that have disrupted Thaipolitics in recent months.

Why was Bhumibol so cautious about the fragile political situation? Contrary to W. Scott Thompson’s comments in his Dec. 10 Times Op-Ed article that Bhumibol has an active role in governing Thailand, the king does not exercise executive authority and does not take sides in Thai politics. Like the queen of England and the emperor of Japan, his authority is symbolic and moral, not political. Even on those occasions when Bhumibol has intervened in a political confrontation, such as the one in 1992, it has been to reduce bloodshed and foster conciliation, not to tell the antagonists what policies to pursue or who should govern.

Bhumibol is the longest-serving monarch in today’s world and one of the longest ever, having reigned for more than 62 years. He has earned the admiration and love of his subjects in a way that Western observers find difficult to describe. He plays a unique role in Thai society as the personification of the Thai nation, as the head of state, as a kindly uncle who encourages the people in good times and bad, as a doer of good deeds and as a spiritual leader who performs sacred rituals.

What he does not do is to meddle in Thai politics. His powers under the many constitutions that have been promulgated since the overthrow of the absolute monarchyin 1932 are strictly limited. Every prime minister must formally seek his endorsement. Similarly, legislation must be signed by him before it takes effect. But such acts are politically neutral; he does not decide who should be prime minister or what policies the government should pursue. Does he favor some leaders over others? Probably. Does it make any difference in deciding political roles or policies? Rarely or never.

Before 1973, Thailand was ruled by a succession of military strongmen; from 1973 to the present, Thailand has been ruled both by military men and democratically elected leaders. The most powerful of these elected leaders was telecommunications billionaire Thaksin Shinawatra, who came to office in 2001 and was overwhelmingly reelected in 2005. But Thaksin overreached in identifying his business interests with the country’s interests, and in early 2006 his family sold its interests in the telecom company for $1.9 billion, virtually tax free, to the Singapore government’s sovereign wealth fund. The protests following this transaction undermined Thaksin’s ability to govern and led to the September 2006 military coup.

This coup was very popular at the time, but it led to a period of weak and indecisive governance, in part because that government lacked an electoral mandate. Subsequentelections brought in remnants of Thaksin’s party but also brought social and political differences to the fore. Demonstrators occupied the grounds of the prime minister’s offices for three months, forcing the cabinets of the period to hold meetings in other places. The last straw was the shutdown of Bangkok’s two main airports for several days, leaving 300,000 travelers stranded and unhappy — a major blow to the vital tourism sector of the Land of Smiles.

The new prime minister, Abhisit Vejjajiva, previously leader of the opposition Democrat Party, received the king’s formal blessing and was sworn in last week, leading a weak coalition government. Abhisit represents a generational change in Thai politics, and he will face serious challenges immediately. What he will not face, however, is interference from the king, who will encourage the new team but will allow it to succeed or fail on the basis of its own performance. The king reigns but does not rule.

Darryl N. Johnson was the U.S. ambassador to Thailand from 2001 to 2004.